The invention is related generally to the field of conduits used as marine drilling riser. More specifically, the invention is related to methods and apparatus for joining together sections of such riser where the riser includes external conduits.
Marine drilling riser is a conduit which extends generally from a valve system (called a xe2x80x9cblowout preventerxe2x80x9d or xe2x80x9cBOPxe2x80x9d stack) disposed on the sea floor up to equipment, typically a drilling rig, disposed on a floating drilling vessel. The riser is used to return drilling fluid (xe2x80x9cmudxe2x80x9d) and drill cuttings from a wellbore drilled through earth formations below the sea floor. Marine drilling riser typically includes a number of auxiliary conduits positioned generally externally to the main pipe or conduit. As is known in the art, the auxiliary conduits, including a choke/kill line, a mud boost line and hydraulic lines, provide communication from the drilling rig to the wellbore through the BOP stack, provide communication to the drilling riser through a riser adapter, and supply hydraulic power to control pods which operate the various control functions on the BOP stack.
Assembling a marine riser, particularly when the auxiliary conduits are used, can be time consuming and expensive. The difficulty in such assembly is a result of the need to keep the auxiliary conduits rotationally fixed. Various connection devices have been developed to increase the speed and efficiency of marine riser assembly where auxiliary conduits are used. For example, U.S. Pat. No. 4,496,173 issued to Roche et al. describes a threaded connector for segments of marine riser which enables the segments (xe2x80x9cjointsxe2x80x9d) of riser to remain rotationally fixed while providing. substantial and evenly distributed axial force to couple the riser joints. Still other connections include flanges which can be bolted together, as explained in the Roche et al. ""173 patent.
Riser connection methods and apparatus known in the art, while effective in reducing the time and expense of riser assembly, require expensive and difficult machining to the riser joints and/or the coupling mechanisms themselves.
It is desirable to have a marine riser connection which enables using conventional threaded couplings between the riser joints while enabling auxiliary conduits to remain rotationally fixed.
The invention is a marine riser segment, which comprises a riser joint having a threaded coupling at each end and flanges disposed on an exterior of the joint. Each of the flanges is coupled to the joint by a bearing. The flanges including openings therein for auxiliary conduits, so that the conduit joint is connectible to another such conduit joint by relative rotation of corresponding ones of the threaded couplings, while the flanges remain rotationally fixed.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.